While there are many manufacturers and suppliers
of roll bars, some of the bars offered on the
market are of poor quality and construction and
could be more of a danger than an asset in an
accident. Here are a few points to observe when
choosing a roll bar to assure you obtain the best
quality available

First, the tubing should have a minimum outside
diameter of 1.5" x .120" thickness in seamless mild
steel for a Spitfire or 1.75" x .120" for a TR6.
The mild steel should have the specification CDS or
DOM. If you want to go absolutely first class, then
a chrome molly alloy steel, SAE 4125, or SAE 4130.
For the maximum protection, T45 should be used. For
home constructed roll bars, mild steel is
recommended due to the welding problems involved in
fabricating chrome molly.

The hoop should be built from on continuous
length of tubing and show no evidence of crimping
at the bends, and have two braces of equal length
attached as close as possible to the top of the
hoop. Certainly, no more than 6" below the top, and
with an inclined angle of 30 degrees. The braces
can be made of slightly smaller diameter than the
main hoop, but certainly no smaller than 3 quarters
of the diameter. A good quality bar usually has the
braces the same diameter.

While most people choose street bars which will
enable them to retain use of the convertible top,
it should be kept in mind that for maximum
protection, the bar should extend above the
driver's head by at least 2". Usually, roll bars
have mounting plates welded to the bottom of them.
The mounting plates should be a minimum of 3/16"
thickness and 4" x 4" with equal size back-up
plates and be attached at each point with four
bolts at least 3/8" in diameter and with a minimum
grade of SAE 5. Welding should be of the heli-arc
type showing a nice, clean continuous bead without
any burn holes or cavities. Also, be sure when
purchasing the roll bar, that the manufacturer
states clearly that the seat travel and top
operation are not effected if that is of
importance.

Usually if a roll bar is purchased through one
of the larger supply houses, the specifications can
be obtained ahead of time and you will not be
disappointed.

Finally, one word of warning. Stay away from low
priced chromium plated roll hoops which are made of
thin tubing and in the event of a serious accident
or roll over, could result in the roll bar wrapping
itself around your neck! Your life is not worth
saving a few bucks!

If you are using you Spitfire for slalom and
gymkhana type events, the organizers may require
additional specifications and if you are
contemplating constructing your own roll bar, then
an excellent source of information is contained in
the SCCA General Competition Rules; Appendix "Z",
from which some of the foregoing information was
extracted.

Remember, this page is meant to general
information only. Always double check with
Sanctioning Bodies for the latest safety
requirements. Remember, your safety should always
be of paramount concern; never a place to save a
few bucks!